these calls reveal realtime reactions when a shooter walked into sandy hook elementary school and killed 21 first graders and six adults. nbc's jay gray has more. >> reporter: the 911 operators were steady and focused as callers described what was going on. a teacher pleading tr help saying somebody's got a gun. i caught a glimpse of somebody running down the hallway still shooting. school custodian described the shattered front window. during the call gun shots rang out in the background. he tells the operator, quote, i keep hearing shooting, i keep hearing popping. then he describes hearing only silence. following the wishes of survivors and family members of the victims, many who fought for nearly a year to block the release of the recordings, nbc will not air the calls. nicole hockley's son died in the attack. she talked with nbc's andrea mitchell this week. >> we don't feel the 911 calls should have been released, but that decision has been made now, and it will affect our community certainly and it will affect our families. >> reporter: but the father of one of the teachers who die